PLATE XXXI. 



Olenellus {Hobnia) walcottanus. 



Fig. I. A nearly perfect specimen crushed flat in the shale and with the exterior 

 shell largely exfoliated. 

 2. A segment of the thorax greatly enlarged, showing the ornamentation of 

 the exterior surface, and on the falcate portion the inosculating lines 

 marking the surface of this portion of the segment. 



(270) 



